2) Power series Flashcards

1
Q

What are the tests for absolute convergence of a series

A
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2
Q

What is the Cauchy-Hadamard test for convergence

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3
Q

What is the Leibniz test for alternating sequences

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4
Q

When does a sequence zn ∈ C converge

A

Let zn ∈ C and write zn = xn +i yn, xn, yn ∈ R. Then the sequence zn converges if and only if both xn and yn converge

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5
Q

What does it mean for a series ∑ zn in C to be absolutely convergent

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6
Q

What is the relationship between absolute convergence and convergence of a series in C

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7
Q

What happens when two absolutely convergent series in C are multiplied

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8
Q

What are the Ratio, Root, and Cauchy-Hadamard tests for convergence in C

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9
Q

What is a power series at z0 in C

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10
Q

What is the radius of convergence R of a power series, and what are its implications

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11
Q

What happens if a power series converges at w and ∣z∣<∣w∣

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12
Q

What is the radius of convergence and the disc of convergence of a power series

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13
Q

What are the formulas for finding the radius of convergence R of a power series

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14
Q

What is the relationship between the radii of convergence of a power series and its derivative

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15
Q

What can be said about the differentiability of a power series within its radius of convergence

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16
Q

What can be said about higher derivatives of a power series within its radius of convergence

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17
Q

What is the relationship between a power series and its integral within the radius of convergence

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18
Q

What can be concluded if two power series are equal within a disc of convergence

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19
Q

How is the exponential function defined as a power series

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20
Q

What is the radius of convergence of the exponential function, and what does it imply

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21
Q

How are the complex sine and cosine functions defined as power series

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22
Q

What is Euler’s formula

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23
Q

How are the hyperbolic cosine and sine functions defined

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24
Q

What are the definitions of cosz, sinz, and their relationships to hyperbolic functions for z,w∈C

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25
Q

What is a period of a function

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26
Q

What is the definition of the complex logarithm

A

Let z ∈ C, z /= 0. Then a complex logarithm of z is log z = log|z| +i arg z where argz is any argument of z

27
Q

What is the cut plane

A
28
Q

What are the properties of the principal logarithm on the cut plane

A

The principal logarithm Log : C− → C is holomorphic
The derivative of the principal logarithm is 1/z